In conventional slip ring assemblies, spaced wire arms of a brush typically ride in a groove disposed on an outer perimeter of a rotating slip ring. Such slip rings are well known to those in the inertial navigation arts and have been used for years in conducting electrical power and signal currents across the pivots of gimbaled systems having freedom of motion used to mount gyroscopes. These prior art slip ring assemblies have been plagued with both manufacture and service use problems causing fairly high removal rates for repair and overhaul. These assemblies are extremely delicate and require high assembly skill and time consuming adjustment to achieve a preload consistent with minimum sliding friction in a vibration and shock-prone environment.
Since such gyroscopic devices generally operate in a vibratory environment, and since sliding contact exists between the brushes and the slip rings, friction polymers tend to build up on the slip rings causing electrical noise and/or open circuits producing an intermittent signal and requiring removal of the slip ring assemblies for cleaning and/or replacement. Furthermore, electrical noise is found in this type of slip ring assembly, and this noise usually is effectively amplified, rendering the signal undesirably noisy, thereby detracting from the signal quality. This noise often is produced by the generation of wear particles between the slip ring and brushes. A third problem often encountered in such assemblies is misalignment of the brushes with respect to the grooved rings resulting from tolerances during assembly. Adjustments to secure a proper fit and loading of brushes at final assembly is not required, thereby eliminating residual stresses in the brushes and subsequent brush load changes with time. Since the brush arms are usually cylindrical, this misalignment causes the brush arms to ride upwardly within the slip ring groove, thereby producing a noisy and/or intermittent signal. Fourthly, the brushes tend to hydroplane on the slip ring surface, especially at high rotational speeds and in the presence of a lubricant. Lastly, the frictional coefficient tends to be high because of the limited choice of satisfactory materials which can be used to serve both as a spring and an electrical contact. The hydroplaning and some of the noise problems may be overcome by increasing the brush loading or elimination of the lubricant, but these changes do not cure the high friction and misalignment problems.
Rolling electrical contact assemblies, such as that shown and described in U.S. Pat. No. 4,068,909 have been developed to overcome some of these problems. However, such assemblies are not suitable for all gyroscopic and inertial system uses, and do not have the wiping action necessary to remove contamination.